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authorAnton Vorontsov <avorontsov@mvista.com>2010-08-24 14:46:12 -0700
committerDavid S. Miller <davem@davemloft.net>2010-08-24 14:46:12 -0700
commitef24b16b5d67c815874ed2d0e2581db629661ba3 (patch)
tree552332dff8d2079695ba0b4b608bc2ad8bf1c3e3 /drivers/net/phy
parent9dc002d8d9c2af837e789b5bb88c61a8b32c1be8 (diff)
downloadlinux-linaro-android-ef24b16b5d67c815874ed2d0e2581db629661ba3.tar.gz
phylib: Fix race between returning phydev and calling adjust_link
It is possible that phylib will call adjust_link before returning from {,of_}phy_connect(), which may cause the following [very rare, though] oops upon reopening the device: Unable to handle kernel paging request for data at address 0x0000024c Oops: Kernel access of bad area, sig: 11 [#1] PREEMPT SMP NR_CPUS=2 LTT NESTING LEVEL : 0 P1021 RDB Modules linked in: NIP: c0345dac LR: c0345dac CTR: c0345d84 TASK = dffab6b0[30] 'events/0' THREAD: c0d24000 CPU: 0 [...] NIP [c0345dac] adjust_link+0x28/0x19c LR [c0345dac] adjust_link+0x28/0x19c Call Trace: [c0d25f00] [000045e1] 0x45e1 (unreliable) [c0d25f30] [c036c158] phy_state_machine+0x3ac/0x554 [...] Here is why. Drivers store phydev in their private structures, e.g. gianfar driver: static int init_phy(struct net_device *dev) { ... priv->phydev = of_phy_connect(...); ... } So that adjust_link could retrieve it back: static void adjust_link(struct net_device *dev) { ... struct phy_device *phydev = priv->phydev; ... } If the device has been opened before, then phydev->state is set to PHY_HALTED (or undefined if the driver didn't call phy_stop()). Now, phy_connect starts the PHY state machine before returning phydev to the driver: phy_start_machine(phydev, NULL); if (phydev->irq > 0) phy_start_interrupts(phydev); return phydev; The time between 'phy_start_machine()' and 'return phydev' is undefined. The start machine routine delays execution for 1 second, which is enough for most cases. But under heavy load, or if you're unlucky, it is quite possible that PHY state machine will execute before phy_connect() returns, and so adjust_link callback will try to dereference phydev, which is not yet ready. To fix the issue, simply initialize the PHY's state to PHY_READY during phy_attach(). This will ensure that phylib won't call adjust_link before phy_start(). Signed-off-by: Anton Vorontsov <avorontsov@mvista.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net/phy')
-rw-r--r--drivers/net/phy/phy_device.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index c0761197c07..16ddc77313c 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -466,6 +466,8 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev,
phydev->interface = interface;
+ phydev->state = PHY_READY;
+
/* Do initial configuration here, now that
* we have certain key parameters
* (dev_flags and interface) */